INVESTIGATION OF THE IRON-CARBON BONDING FOR ALKYL, ALKYNYL, CARBENE,VINYLIDENE, AND ALLENYLIDENE COMPLEXES USING FE-57 MOSSBAUER-SPECTROSCOPY

The synthesis of the iron allenylidene [Cp(dppe)Fe(=C=C=C(OCH3)CH3)][ BPh4] (7) was achieved in one step, from the reaction of the Cp(dppe) FeCl (8) with 1 equiv. of Me-3-Si-C=C-C=CH. By working in methanol and in the presence of NaBPh4, the complex 7 was isolated in 85% yield as a dark green powder. Comparison of the Mossbauer parameters of a seri es of 16 compounds having the same Cp(dppe)Fe backbone and a end-boun d hydrocarbon ligand shows that it is possible to identify both the ox idation state of the metal (Fe-II vs. Fe-III) and the metal-carbon bon ding (single vs. double bond) of the terminal hydrocarbon ligands usin g Mossbauer spectroscopy. (C) 1998 Elsevier Science S.A. All rights re served.